The _sample_ is flawed because H-1B visa holders are atypical. In some situations they are hired precisely because they have lower salary expectations than US residents (paying them less than the prevailing rate violates the terms of their Labor Condition Application, but it happens). In other situations the employer puts up the with expense and delay of the visa application because they have unique skills that also make them more valuable.
The _data_ itself is flawed because the salary information is only recorded at the time the offer was made, since which it has presumably increased, and it does not include bonuses or non-cash compensation.
They just have my base salary listed there, which is a super-inaccurate way to compare salaries, in my opinion. RSUs and bonus are almost 50% of my comp. They also have my starting salary there, no increases, etc since then.